Question

These static Array methods have me puzzled. They seem to do the same things. Are they available for older legacy code?

Array.IndexOf
Array.FindIndex

Array.LastIndexOf
Array.FindLastIndex

Answer 1

One accepts an item to match. The other other accepts a function that checks an item and return true if matches, false if it does not.

For example:

var x = {1,2,3,4,5,6};
int i = Array.IndexOf(x, 2);
int j = Array.FindIndex(x, a => a == 2);